Cognitive decline and cognitive impairment are common in older adults and are associated with significant morbidity and mortality. However, few interventions have been identified to prevent or delay cognitive decline. Widespread environmental pollutants may be related to cognitive decline in later years through neurotoxic effects or adverse effects on cardiovascular health and are potentially modifiable. If a causal relationship exists, intervention on such risk factors would have substantial benefits. The proposed work will explore whether exposures to two common environmental pollutants, lead and traffic-related air pollution, are associated with cognitive decline. Evaluation of the relationship between lead and change in cognitive test performance over time will be conducted using a subset of participants in the Nurses' Health Study (NHS), a cohort of community-dwelling older women. Generalized estimating equations will be used to evaluate whether higher levels of lead biomarkers are adversely associated with change in cognitive test performance over time. In addition, menopause-related bone mineral density releases lead previously stored in bone into the systemic circulation and may increase the vulnerability of women to the adverse effects of past lead exposure. To evaluate the whether recent exposures, including menopause-related reintroduction of lead, is associated with greater declines in cognitive function in postmenopausal women, the relationship between blood lead levels and change in cognitive performance over time will be assessed in a subset of women whose blood lead measurements reflect exposure during this critical period. Evaluation of the relationship between traffic-related air pollution and cognitive test performance will be conducted in subset of participants in the Normative Aging Study (NAS), a cohort of older men. Mixed models will be used to evaluate whether higher levels of exposure to black carbon, estimated using a validated spatiotemporal land-use regression model, have an adverse effect on the level or the change in cognitive performance over time. Understanding the role of these exposures on cognitive function may suggest beneficial interventions and help to elucidate the underlying biologic processes of this detrimental condition. PUBLIC HEALTH RELEVANCE: Identification of and intervention on modifiable risk factors for cognitive decline in older adults would be expected to have significant benefits. If exposure to lead or air pollution is related to cognitive decline, interventions to lessen exposure, including increasing bone health or regulation of pollutants would be beneficial. In addition, identification of risk factors for cognitive decline may provide valuable insight into the underlying biological mechanisms for initiation and progression of cognitive decline and the associated disease state of dementia. )